The present invention relates to a gas compressor for use in a car cooler and, more particularly, to a gas compressor in which the capacity of its compression chamber is made variable.
Usually, a gas compressor used for cooling an automobile or the like is arranged in parallel with an engine so that the gas compressor is driven through a V-belt by the crankshaft pulley of the engine, and the gas compressor is connected to or disconnected from the drive side means of an electromagnetic clutch which is disposed in the compressor side.
As a result, the capacity of the gas compressor of the above-specified type is increased in proportion to the r.p.m. of the engine. This in turn causes the gas compressor to be driven at a high speed, in case the automobile runs at a high speed, thereby to over-cool the automobile compartment and to raise a defect that the power consumption is increased in proportion to the running speed. This tendency is serious especially in the gas compressor of rotary type.
In order to eliminate this defect, there have been proposed a variety of the so-called "volume-variable type" gas compressors in which the volume of a coolant gas in the compression chamber is regulated in accordance with the driving speed.
For example, the volume of the coolant gas is made variable by controlling the opening of a bypass hole, which is formed in a position suitably displaced in the rotational direction of a rotor with respect to an intake port.
In the gas compressor of this type, however, the coolant gas once confined in the compression chamber is bypassed to an intake side after the coolant gas has been compressed to some extent. Therefore, the gas compressor has an inferior compression efficiency and a drawback that the discharge temperature of the coolant gas rises especially at the high-speed, i.e., small-volume run.
Incidentally, the gas compressor developed in recent years is of the type, in which the volume of an intake to be sucked from an intake fluid port of a front side block of the compressor is made variable by mounting a rotary plate in the front side. The rotary plate is formed with a recess communicating with the intake port, and by rotating the rotary plate a predetermined angle the volume of the intake fluid is regulated. In the gas compressor of this type, most of the means for controlling the rotary plate are constructed such that the temperature of the air in of the automobile compartment or an evaporator is sensed by means of a thermostat so that the rotary plate can be turned by the drive of a motor attached to the compressor when the temperature drops to or lower than a set level of the thermostat. This raises defects that the construction is complicated and large-sized by the added motor.
For example, in U.S. Pat. No. 4137018, it is disclosed that a control plate is mounted between a cylinder and a front side block, and that the shaft 220 which gears with the control plate 200 drives the control plate 200.
In this mechanism, however, another drive means for driving shaft 220 is needed. Although it is not described in this patent that this mechanism is controlled automatically, if the control plate 200 were controlled automatically, the mechanism would be complex wholly, and would not be simplified and made compact.